1. Field of the Invention
The present invention relates to an instant photo film pack. More particularly, the present invention relates to an instant photo film pack which includes plastic parts with minimized use of other materials, so as to facilitate abandonment after being used.
2. Description Related to the Prior Art
A self-developing photo film unit is known, examples of which are a mono-sheet type and a peel-apart type. U.S. Pat. No. 4,637,703 (corresponding to JP-Y (Japanese Utility Model Publication No.) 5-62725) discloses the peel-apart type, which includes a photosensitive sheet and an image receiving sheet contained in a pack case in a manner spaced from one another. After the photosensitive sheet is exposed, the photo film unit is advanced by a pair of spreader rollers between them by pulling out of a withdrawing sheet. The photosensitive sheet and an image receiving sheet are laid on one another by the advancing operation. Furthermore a developing solution pod is squeezed to spread the developing solution between the photosensitive sheet and an image receiving sheet.
In FIG. 5, an instant photo film pack for containing self-developing photo film units of the peel-apart type is illustrated. A pack case 2 is constituted by a pack body 4 and a bottom cover member 6. The pack body 4 is an upper component and has a box shape of a substantially rectangular parallelepiped. The bottom cover 6 is a bottom component closing a bottom opening of the pack body 4. A pressure plate 5 is contained between the pack body 4 and the bottom cover 6. There is an exposure opening 3 formed in the pack body 4. The pack body 4 is a plastic molded piece molded by injection molding, which is advantageous in that ambient light can be effectively shielded at corners of the pack body 4, and that the pack body 4 can be produced at a low cost. A bottom edge of an end wall 7 with a passage opening is in such a position that its level is higher than a bottom edge of an end wall or lateral side walls, so that the passage opening for advance of the photo film units is defined under the end wall 7 when the bottom cover 6 is secured to the pack body 4.
Ridges 8 are formed with respectively lateral walls of the pack body 4. Cutouts 9 are formed in the bottoms of the lateral walls of the pack body 4 and located under the ridges 8. The pressure plate 5 is produced according to pressing from a thin plate of metal. A front edge of a flat middle wall 11 is provided with a retaining portion 12 for photo film units. A curved portion 13 is disposed on a rear edge of the flat middle wall 11. First and second lateral walls 14 are disposed on lateral sides of the flat middle wall 11 and oriented vertically downwards by bending. There are a pair of retaining holes 12a formed in the end of the retaining portion 12, for the purpose of retention of ends of the photo film units.
The bottom cover 6 is formed according to pressing from a thin plate of metal. A middle wall 15 of the bottom cover 6 is provided with lateral walls 16 disposed along its lateral sides. Top edges of the lateral walls 16 are bent in inward directions. When the bottom cover 6 is mounted on the pack body 4 by sliding the bottom cover 6 along bottom edges of the pack body 4, the ridges 8 on lateral walls of the pack body 4 are covered by the lateral walls 16 before the bottom cover 6 is connected with the pack body 4.
Spring portions 18 are formed by bending, and disposed on the lateral sides of the middle wall 15. When the pressure plate 5 is contained in the pack body 4 and the bottom cover 6 is secured to the pack body 4, the spring portions 18 push up bottom edges of the first and second lateral walls 14, and bias the pressure plate 5 toward the exposure opening 3. A recess 19 is formed in a front edge of the middle wall 15. A sponge pad 20 is secured to the inside of the recess 19 and protrudes in a withdrawing direction.
The sponge pad 20 is constituted by a paper base member and a part of sponge or polyurethane foam attached to a top face of the paper base member. As will be described later, the sponge pad 20 keeps an image receiving sheet from moving before a photosensitive sheet moves to a predetermined position in the course of withdrawal of each exposed photo film unit.
An instant photo film pack 21 is constituted by the pack case 2 and the photo film units contained in the pack case 2. In FIG. 6, the instant photo film pack 21, when used, is loaded in a pack holder 24. The pack holder 24 is also referred to as a camera back, and includes a first plate 30 and a second plate 27 of a holder body. The second plate 27 is provided with a roller assembly 26 including a pair of spreader rollers 25. The first plate 30 is connected with the second plate 27 in a manner rotatable about a pivot 28. A holder opening 30a is formed in the first plate 30, which is used in such a state that a surface of the first plate 30 is tightly contacted by a back surface of an instant camera. Also there is a ridge 30b adapted to positioning of the pack holder 24 on the back of the instant camera.
In FIG. 6, first and second spring portions 35 of a spring plate push the bottom cover 6 of the instant photo film pack 21, and keep the instant photo film pack 21 pushed upwards. Thus a top face of the pack case 2 is pressed against an upper inside face of a pack support frame 32, so as to position the instant photo film pack 21 suitably in a direction parallel to an optical axis of a photographic light path.
As is well-known in the art, a self-developing photo film unit includes a photosensitive sheet 40 and an image receiving sheet 41, which are contained respectively above and below the pressure plate 5 inside the pack case 2. When all of the stacked photo film units are unused, the exposure opening 3 is closed by a light-shielding sheet 42. There are 10 photo film units contained in the pack case 2. But only one photo film unit is depicted in FIG. 6 with the light-shielding sheet 42 for the purpose of simplification of the depiction. A withdrawing sheet 43 is connected with the photosensitive sheet 40 and the image receiving sheet 41. The photosensitive sheet 40 is located between the exposure opening 3 and the pressure plate 5. The image receiving sheet 41 is disposed under the pressure plate 5 and oriented downwards.
There is a tab exit slot 44, which is defined between the second plate 27 and the first plate 30, and through which a distal end of the light-shielding sheet 42 is protruded when the instant photo film pack 21 is contained in the pack holder 24. A remaining end of the light-shielding sheet 42 is fastened to the pressure plate 5 together with the photo film units by staples or wire chips used with a stapler. When the protruding distal end at the tab exit slot 44 is manually drawn out, the remaining end of the light-shielding sheet 42 is torn away from the staple-fastened portion by means of a perforation line or notches, so that the light-shielding sheet 42 is separated and withdrawn out of the tab exit slot 44 as one sheet. Thus a first one of the photosensitive sheets 40 comes to lie on the exposure opening 3 and becomes ready for being exposed. The distal end of the light-shielding sheet 42 is provided with a tab 45 of the first photo film unit. The tab 45 has one end attached to one end of the withdrawing sheet 43 of the photo film unit. When the light-shielding sheet 42 is removed, the end of the tab 45 comes to protrude from the tab exit slot 44.
The spring portions 18 on the middle wall 15 of the pack case 2 contact bottom edges of the first and second lateral walls 14 of the pressure plate 5, which is kept pushed up by the spring portions 18. Thus the photosensitive sheet 40 is moved up with the pressure plate 5, and pressed against an upper inside face of the pack case 2. The photosensitive sheet 40 remains positioned constantly inside the pack case 2 in a state ready to be exposed.
The tab 45 is manually pulled out after an exposure is taken through the holder opening 30a of the pack holder 24 and the exposure opening 3 of the pack case 2. The withdrawing sheet 43 is caused to move to the spreader rollers 25. As indicated by the phantom line, an end of the withdrawing sheet 43 is moved between the spreader rollers 25, pushes open the exit door at a photo film exit slot 38 and exits through the photo film exit slot 38. At this time, the attached portion of the tab 45 to the withdrawing sheet 43 is located directly under the tab exit slot 44. Therefore the force of pulling the tab 45 peels the tab 45 from the withdrawing sheet 43. When the tab 45 of the first photo film unit is completely peeled, the tab 45 of a second one of the photo film units comes to appear through the tab exit slot 44.
Then the withdrawing sheet 43 partially protruded from between the spreader rollers 25 is manually pinched and withdrawn. The photosensitive sheet 40 is moved horizontally to the left in the drawing, is turned back at the curved portion 13 of the pressure plate 5, and is moved to the bottom of the pressure plate 5. Now the exposed surface of the photosensitive sheet 40 is oriented downwards. A developing solution pod 46, which is disposed on the withdrawing sheet 43, is moved past the image receiving sheet 41 and comes nearer to the spreader rollers 25. There is a connector sheet 47 or mask sheet connecting the image receiving sheet 41 with the withdrawing sheet 43. When the mask sheet 47 is spread and fully unfolded, the exposed surface of the photosensitive sheet 40 comes to a position opposite to the image receiving sheet 41. The force of withdrawing the withdrawing sheet 43 causes the combination of the photosensitive sheet 40 and the image receiving sheet 41 to be moved toward the spreader rollers 25.
In the course of movement of the photosensitive sheet 40 to the image receiving sheet 41 in unfolding of the mask sheet 47, pressure and friction of the sponge pad 20 keep the image receiving sheet 41 from moving. Therefore the photosensitive sheet 40 and the image receiving sheet 41 are caused by the sponge pad 20 to lie completely on one another when moved to the position between the spreader rollers 25.
Shortly before the photosensitive sheet 40 and the image receiving sheet 41 come to a position between the spreader rollers 25, the solution pod 46 is squeezed by the spreader rollers 25. The developing solution in the solution pod 46 is spread between the photosensitive sheet 40 and the image receiving sheet 41 at a regularized thickness. After each photo film unit is completely pulled out of the spreader rollers 25, a predetermined time for development and fixation is elapsed. Then a positive image appears on the image receiving sheet 41, which is peeled away from the photo film unit to become a photographic print.
In the pack case 2 according to the prior art for containing the peel-apart type of photo film units, the spring portions 18 as portions of the bottom cover 6 of metal are essentially operated for pressing the pressure plate 5 toward the exposure opening 3 to position each photosensitive sheet. Also the sponge pad 20 on the bottom cover 6 is important at the time of pulling the withdrawing sheet 43 after an exposure, because the photosensitive sheet 40 and the image receiving sheet 41 must be advanced to the spreader rollers 25 after laying them on each other.
In accordance with the above construction, parts of the pack case 2 include various materials, such as metal, plastics, paper and sponge. The pack case 2 after using the photo film units is discarded as a waste. As the pack case 2 is a combination of the various materials, users must disassemble the pack case 2 and discard the parts in a classified manner. This is a laborious operation caused by the structure of the pack case 2. Also the users' hands are likely to be injured when disassembling the pack case 2.
In the manufacturing process of the instant photo film pack 21, the bottom cover 6 is finally mounted on the pack body 4 by sliding operation via the end wall of the pack body 4. It is likely that an edge of the bottom cover 6 of metal partially scratches the pack body 4 of the plastic material or the light-shielding sheet 42 of paper. Dust or particles may be created by scratching and scattered inside the pack case 2 to cause problems in taking an exposure or spreading the developing solution. For example, unexposed spots shaped like pinholes may be formed or spreading irregularities may occur. Also, users' hands are likely to be wounded by contact with the edges of the bottom cover 6 or metal part when they remove the instant photo film pack 21 from a packaging bag, because the edges of the metal part are tapered.
The pressure plate 5 and the bottom cover 6 are metal parts causing the instant photo film pack 21 to have a great weight. If the instant photo film pack 21 is dropped accidentally, the bottom cover 6 may be deformed by shock. The light-shielding sheet 42 and the photo film units are likely to be damaged, because they are broken away at portions fastened with staples or wire chips. If the instant photo film pack 21 is dropped with a packaging bag, corners of the metal parts are likely to strike and perforate the packaging bag, of which moisture-tightness is damaged. If the damaged packaging bag is still used, the photo film units in the instant photo film pack 21 are degraded inevitably.
If one desires abandonment of the pack case 2 without classification of parts, the pack body 4, the pressure plate 5 and the bottom cover 6 must be produced from the same material. However paper is not suitable for such material, because the spring portions 18 of the bottom cover 6 cannot easily have a resilient characteristic required for a spring. Also the absorbing operation of the sponge pad 20 cannot be easily obtained from paper material. There is a problem in that the use of paper is likely to create dust or powder in the course of manufacture. Furthermore, metal is not suitable as the common material for the pack case 2 including the pack body 4. The pack body 4 would be constituted by a bent form of a thin plate of metal. It is difficult to shield corners of the pack body 4 from ambient light. The large amount of weight and high manufacturing cost of the pack body 4 are also disadvantageous.
Should the pressure plate 5 and the bottom cover 6 be both plastic, no biasing operation of the spring portions 18 cannot be obtained only with resiliency of the plastic parts. Even if a first one of the photo film units is safely pressed to the exposure opening 3 by such plastic parts, succeeding ones of the photo film units may be insufficiently pressed, because the plastic parts exert only a biasing force smaller than that exerted to the first photo film unit. There occurs imprecision with which the photosensitive sheet of the succeeding photo film units is positioned in a direction of an photographic optical axis. Photographs cannot be taken in a sharply focused manner.